The present invention relates to a method of fabricating an air-bag and more particularly relates to an air-bag which, when inflated, is intended to be located between the head or body of the driver or front-seat occupant of the motor vehicle and the adjacent window. Such an air-bag may be termed a side-curtain and may be adapted to be inflated in the event that a side impact or roll-over situation should occur. A side-curtain may extend adjacent the head of the driver or front seat occupant of the motor vehicle, or may extend from the front of the vehicle to the rear of the motor vehicle, along the side of the vehicle, thus providing protection, not only for the driver or front seat occupant of the vehicle, but also for an occupant of the rear seat of the vehicle.
A side-curtain has to be deployed extremely rapidly if it is to provide protection in the event that a side impact should occur and consequently the side-curtain is inflated by injecting a large quantity of gas into the side-curtain very rapidly. The inflation consequently violent, and the fabric may stretch at certain points.
In order to improve the gas-tightness of the fabric that makes an air-bag, it is conventional to provide the fabric with a coating of a sealant material such as a silicone rubber. In certain air-bags, such as air-bags intended to provide protection for the driver or front seat occupant of the vehicle in the event that a front impact should occur, the air-bag is initially fabricated with the coating on the exterior of the air-bag, and then the air-bag is turned inside-out before being installed in the motor vehicle so that the coating is then on the interior of the air-bags. In the event that the air-bag is inflated, the gas that is injected into the air-bag tends to urge the coating into firm contact with the yarns constituting the fabric from which the air-bag is made, ensuring that any small gap that might exist between the yarns is sealed, consequently ensuring the integrity and gas-tightness of the air-bag. This is important, since in many instances an inert gas of low atomic weight is utilised to inflate the air-bag, and such a gas can easily pass through very small interstices between adjacent yarns. The coating also protects the fabric from the hot gas that maybe present in the air-bag when it is inflated. The strength of the fabric maybe reduced if the fabric is not protected from the hot gases.
In the case of a side-curtain, however, the air-bag is of a complex form and can not readily be turned inside-out. Consequently, the coating has to be applied to the exterior of the air-bag. This means that the pressure of gas present within the air-bag when it is inflated tends to dislodge the coating from the exterior of the air-bag, rather than press the coating more firmly into the interstices of the fabric. Also, as the bag is inflated the fabric from which the bag is made may stretch, especially in areas where high stresses are applied to the bag, and this may cause the coating to become dislodged from the fabric. For these reasons the coating is often relatively heavy and may be applied at a rate of 130 grams per square meter. This not only increases the weight of the air-bag, but substantially increases the cost, since the silicone rubber material is expensive. Also the lack of an internal coating means that the fabric of the air-bag will not be protected from the hot gasses.
It has been found that the silicone rubber applied to the exterior of the air-bag provides various disadvantages in that the silicone rubber is tacky and therefore exerts a high friction. Consequently, during deployment of the air-bag, the air-bag may stick to the glass or the material forming the “B”-Post of the vehicle, thus leading to distortion of the air-bag during the inflation process. Should the air-bag contact the passenger or occupant of the vehicle during the inflation process, the air-bag may impart an abrasion wound.